The present invention relates to the structure of a capacitor and, more particularly, to the structure of a feed-through capacitor.
In a capacitor of the type in which an electrical conductor is a through dielectric element as named hereinafter, a feed-through capacitor, it is desired that without changing the external size of the capacitor, the electrostatic capacity be controlled. FIG. 1 shows a longitudinally sectional view of an example of such a feed-through capacitor.
Reffering to FIG. 1, a feed-through capacitor 1 includes a tube-shaped dielectric material 2. At the upper protions of the tube-shaped dielectric material 2, a flange portion 2a is formed for supporting the feed-through capacitor 1 on a chassis. To surround the tube-shaped dielectric material 2, an inner electrode 3 and an outer electrode 4 are provided. Surrounded by the inside of the tube-shaped dielectric material 2, an aperture 5 is formed within which an electrically conductive central shaft 6 is inserted.
To make the electrostatic capacity large without changing the exterior sizes of the feed-through capacitor, the diameter of the aperture 5 should be made larger and the diameter of the tube-shaped dielectric material 2 should be smaller. Because of this intention, the lower portions of the tube-shaped dielectric material 2 is made brittle, so that these portions may be damaged, in particular, during forming the inner and the outer electrodes 3 and 4. Further, a soldering material 7 may be introduced within the aperture 5 for fixing the electrically conductive central shaft 6 within the aperture 5 by curing the soldering material 7. In such a case, the fixed soldering material 7 may be resolved owing to the heat in positioning the feed-through capacitor 1 on a chassis with a soldering material, so that the electrically conductive central shaft 6 may be dropped from the soldering material 7. A washer 8 may be inserted.
If the tube-shaped dielectric material 2 becomes thin, the feed-through capacitor 1 may be damaged by external stress.